B7800 Won't Start Electrical Problem

[Minerboyd]

I have a B7800 that was blowing the 5 Amp fuse labeled "Key Off", it started bowing when I lowered the front bucket with a sharp bouncing movement, before I could verify what was causing the fuse to blow, it began blowing when we would simply start to move the tractor forwards or backwards. It got to the point where I could replace the fuse start the engine and as soon as I tried to move it backwards the fuse would blow again as soon as it started to move. In desperation to get it out of my driveway, I did what I knew I shouldn't have done and I wrapped a tiny wire around the fuse hoping to keep the engine running at least long enough to back it out of my driveway five feet, instead of blowing the fuse this time, I blew/damaged something else. Now the fuse appears to be fine but I am getting no power to the dash lights or key, it is acting exactly the same as it was before when only the 5 amp fuse had been blown. (The problem is that now the 5 amp fuse is fine, and it is something else that is preventing the key and dash panel from getting any power or lights). I tracked the wire from the 5 amp fuse into what looks like a solid state resistor or what the wiring diagram calls a "Controller", Part Number: K3511-55222. I am wondering if this controller can be tested to find out if I damaged it when I shorted out the 5 amp fuse with the wire. If it can be tested which wires do I test and what am I looking for when I test them? I am also wondering what else might have been able to cause the 5 amp fuse to blow every time I tried to move the tractor. I have read that there are two diodes somewhere in the safety switch circuit of this tractor located somewhere between the HST pedal and the clutch switch that could cause the 5 amp fuse to be blown if they are not working correctly. I have not been able to locate the "Clutch Switch" anywhere on my tractor does anyone know where it is located and what it looks like? Also could anyone tell me where I could find these diodes and how to test them so I can determine if it was one of these diodes that was causing the 5 amp fuse to be blown in the first place. Anything else that I may have missed that could have caused the 5 amp fuse to be blown every time I tried to move the tractor as well as any instructions on how to test them to verify that it was part of or all of the problem will be appreciated.

 

[cerlawson]

Before doing more, see if Messicks have a shop manual with electrical diagram.

www.messicks.com

That should help a lot.

For my smaller BX there are no fuses as small as 5 amp.

 

[Daren Todd]

If you check out tractor won't start, wolfman posted about a main fuse by the starter. May have blown that when you bypassed the fuse. And a quick check any where your wiring harness goes near the engine block, or a pinch point wouldn't hurt. Had all sorts of weird electrical issues when i got my bota a few weeks ago. Ended up finding some wires that had come in contact with the engine block and melted down.

 

[rentthis]

I had the same problem with a similar tractor. The fuse would blow when the tractor was moved and turned to the left. It was a wire with the insulation worn and grounding to the frame. It was a pain to find. My son it really great with that sort of thing so I left the job to him. The 5 amp fuse narrowed the search to that circuit and make it a little easier to find. The problem was somewhere in the vicinity of the clutch pedal. I'm sorry not to be able to be more specific but what are the chances of it being the same wire anyway? The problem was triggered by the flex in the machine when it moved.

 

[ShaunRH]

Sounds like I should invest in some silicone sleeves to put around the wire harnesses of my new L3200...

I hate electrical problems with a passion and don't want any like this to show up... ugh!

I wonder why Kubota doesn't provide a little more protection or stress relief in their harnesses...